What is the order of current flowing in the nerves of our body?

The charge flowing in a conductor varies with time as $Q = at - bt^2$. Then for current,which statement is incorrect?
$(A)$ decreases linearly with time
$(B)$ reaches a maximum and then decreases
$(C)$ falls to zero after time $t = a/2b$
$(D)$ changes at a rate $-2b$

Due to what is current formed in conductors?

An electron revolves $6 \times 10^{15}$ times per second in a circular loop. The current in the loop is:

The current in a conductor varies with time $t$ as $I = 2t + 3t^2$,where $I$ is in ampere and $t$ is in seconds. The electric charge flowing through a section of the conductor during $t = 2 \, s$ to $t = 3 \, s$ is ............. $C$.

The charge of an electron is $1.6 \times 10^{-19} \ C$. How many electrons strike the screen of a cathode ray tube each second when the beam current is $16 \ mA$?